Flagellar apparatus and evolution of the peronosporomycetidae (oomycota)

卵菌是一种类似真菌的生物，也被称为水霉菌。大多数物种可以产生游动孢子，游动孢子在游动孢子的同一点上有两个不同的鞭毛。在卵菌中发现的两个亚类中，大多数是引起植物疾病或生长在死亡有机物上的陆生物种，是本次研究的目标亚类。主要的两个属是腐霉属和疫霉属。如果有足够的自由水存在，这在暴雨后的农业土壤中很常见，游动孢子可以通过感知化学物质或电荷的变化而主动游向宿主的根部。如果根部受伤，这种定向运动尤其明显。有趣的是，虽然有几种腐霉，特别是疫霉只能感染某些物种，但游动孢子在游向根系时似乎无法感觉到宿主是否合适。游动孢子到达宿主后，许多分子研究一直在研究植物/病原菌的相互作用，因为这是许多有趣的基因相互作用的地方，导致抗性或疾病后果。然而，很少有分子研究将精力集中在游动孢子本身。我们的实验室在腐霉的分类和分子生态学方面拥有广泛的专业知识。我们希望找到与游动孢子的鞭毛器、运动性和行为有关的独特基因，并在腐霉属物种中比较这些基因序列。我们将关闭隐皮腐霉中的一些基因，并观察它们对游动孢子的影响。我们已经开发了各种工具来检测环境中的腐霉物种，但它们无法区分被检测到的腐霉组织的种类，也无法区分病原体是否处于休眠状态。一旦我们确定了在活跃的游动孢子中或当游动孢子产生时专门表达的基因，我们将能够通过检测游动孢子的活跃RNA和鉴定从哪个腐霉物种中分离出RNA来改进我们开发的系统，从而有可能准确地预测一个作物物种是否处于危险之中。这将是我们的诊断系统在商业上使用的一个重大改进。

The oomycetes are fungus-like organisms also called water moulds. Most species can produce zoospores that swim in water with two different flagella attached at the same point on the zoospore. Most species of the Peronosporomycetidae, the targeted subclass for this study out of the two found in oomycetes, are terrestrial species causing diseases of plants or growing on dead organic matter. The two main genera are Pythium and Phytophthora. If enough free water is present, which is common in agricultural soil after heavy rain, the zoospores can actively swim towards the roots of a host by sensing changes in chemicals or electric charges. This directional movement is particularly noticeable if the roots are wounded. Interestingly, although several species of Pythium and particularly Phytophthora can only infect certain species, the zoospores do not seem to be able to sense if a host is suitable or not when they are swimming towards a root system. Many molecular studies have been dealing with the plant/pathogen interactions once the zoospore has reached the host since this is where many interesting gene for gene interactions occur leading to resistance or disease outcomes. However, few molecular studies have concentrated their efforts on the zoospore itself. Our laboratory has extensive expertise in taxonomy and molecular ecology of Pythium. We want to find unique genes involved in the flagellar apparatus, motility and behaviour of the zoospore and compared these gene sequences among Pythium species. We will turn off some of these genes in Pythium aphanidermatum and see their effect on zoospore. We have developed various tools to detect Pythium species in the environment but they cannot differentiate the kind of Pythium tissue being detected or if the pathogen is dormant or not. Once we have identified genes expressed exclusively in active zoospores or when the zoospores are being produced, we will be able to improve the systems we have developed by detecting RNA of active of zoospores and identifying the Pythium species from which the RNA was isolated, making it possible to predict accurately if a crop species is at risk or not. This would be a significant improvement of our diagnostics system being used commercially.